3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) (i.e., the improvement of a Universal Mobile Telecommunications System (UMTS)) is introduced as 3GPP release 8. 3GPP LTE uses Orthogonal Frequency Division Multiple Access (OFDMA) in downlink and uses Single Carrier-Frequency Division Multiple Access (SC-FDMA) in uplink. Multiple Input Multiple Output (MIMO) having a maximum of 4 antennas is adopted. Recently, a discussion on 3GPP LTE-Advanced (LTE-A) which is the evolution of 3GPP LTE is in progress.
Technology introduced in 3GPP LTE-A includes a carrier aggregation, a relay, etc. A 3GPP LTE system is a single carrier system that supports only one bandwidth (i.e., one component carrier) of {1.4, 3, 5, 10, 15, 20} MHz. However, LTE-A is introducing multiple carriers employing a carrier aggregation. A component carrier is defined by a center frequency and a bandwidth. A multiple carrier system uses a plurality of component carriers having a smaller bandwidth than the entire bandwidth.
As a plurality of component carriers is used, backward compatibility with the existing system need to be guaranteed in some component carriers, but some component carriers may be designed to have higher efficiency without taking backward compatibility into consideration.
Synchronization acquisition is that user equipment performs synchronization for accessing a base station. In a multiple carrier system where various types of component carriers coexist, there is a need for a method of user equipment acquiring synchronization.